Research On The Polarization And Sensing Of Linearly Chirped Fiber Bragg Gratings

LCFBG is short for the linear chirped fiber grating. It has a similar structurecompared with uniform fiber grating. In the meanwhile its grating period can changelinearly along the longitudinal direction. Because of this characteristic, chirped fiberBragg grating (CFBG) can reflect the incident light with continuous wavelength and iswidely used particularly in the field of optical fiber communications.In this paper, on the basis of the method of existing transmission matrix andtheories of chirped grating provided by previous researchers, systematic analysis ofCFBG has been done. The researcher combines numerical simulation with experimentfor this study.Firstly, according to optics and existing theories, the polarization characteristicshave been researched. On the other hand, the researcher uses the theory of the chirpedgrating theory to state the relationship between the various parameters.Secondly, the researcher does further discussion about effects on the chirpedreflection spectrum and PDL which arise from parameters. The impact of variousparameters on the polarization spectrum is analyzed. The results show that theparameter of grating length has a big effect on the spectrum of the CFBG.Finally, the thesis researched the influence of the axial stress to chirped fibergrating reflectance spectrum and the PDL by combined experiment and theory. Throughthe studying to chirped fiber grating theory, we can infer that the axial stress can changemany physical quantities, such as the grating period, effective refractive index, the corerefractive index and so on, and the nature of the axial stress made the variation of therefractive index modulation depth. A mass of experiment results indicated that thereflectance spectrum of chirped blagg fiber grating is closely related to the axial stress,the reflectance spectrum will red shift with increasing the axial stress; PDL is also beeninfluenced by the axial stress, the PDL also will red shift with increasing the axial stress.The polarization property of chirped fiber grating is sensitive to the stress, it makes thatchirped fiber grating is potential for applying to stress sense.